DEVICE TO DETERMINE DIRECT AND REVERSE SEQUENCES OF MAIN AND HIGHER HARMONICS OF SIGNALS IN THREE-PHASE NETWORKS Russian patent published in 2013 - IPC G01R29/16 

FIELD: measurement equipment.

SUBSTANCE: device to detect direct and reverse sequences of main and higher harmonics of signals in three-phase networks comprises a direct Clark converter and a frequency self-tuning system (FSTS), the first and second subtractors, a filter of direct sequence and a filter of reverse sequence, the first and second reverse Clark converters, a detector of period start, a control device, a multiplier, a primary buffer, a buffer of first harmonics, a unit of calculation and indication. The direct Clark converter converts signals from a three-phase abc - system into a two-phase ap-system. FSTS tunes clock frequency of a device with a frequency of measured signals. In the initial period after operations of digitisation and quantisation instantaneous values of the signal are recorded into a primary buffer. In the beginning of the second period the data from the primary buffer is supplied to inputs of subtractors, and instantaneous values of the second period signal are recorded into the primary buffer. Within the second period the main and higher harmonics are analysed. The start period detector detects the moment of period start, at the same time instantaneous values of the signal are registered in the primary buffer and arrive to the inputs of the first and second subtractors. The control device starts a cycle of calculations, starting from the main harmonic, and sets a signal at the output, which corresponds to the first harmonic. Upon detection of main harmonic direct and reverse sequence parameters, direct and reverse sequences of higher harmonics are analysed. With the start of a new period the process is repeated.

EFFECT: increased accuracy of measurement and simplified circuit.

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